In the pulp and paper industry, the chipping of wood is performed by means of centrifugal or rotary wood chipping apparatus, often commonly referred to as disc chippers. Disc chippers reduce logs that are introduced, either at least partially vertically under the aid of gravity or conveyed horizontally, into a feed spout or chute of the apparatus. The logs are passed in relation to a cutting disc element that is rotated about an axis, the disc element having a plurality of radial cutting surfaces (e.g., knives) that chip the logs against a fixed bedknife (also commonly referred to as an anvil or counterblade) that is fastened to the chipper frame and disposed in relation to the lower or rear portion of the feed spout.
In operation, the cutting disc element is caused to rotate about its axis by means of a drive mechanism and the logs entering the feed spout slide against the bedknife and are effectively reduced into chips that pass through openings provided in the cutting disc, as shown for example in FIG. 7.
Based on the present design of such apparatus, it is possible that a number of long thin longitudinal strips or slivers are formed from the cutting operation. The creation of slivers can drastically impede upon the throughput of the chipper, requiring undesired maintenance to remove them from the apparatus as well as additional equipment to remove the slivers and further process this objectionable product from the chips produced. To that end, efforts have been made in the prior art in order to reduce the size or incidence of slivers, such as by incorporation of sliver rings. These assemblies are useful in preventing slivers from reaching a predetermined size, but these features do not actually reduce the overall incidence of slivers. Other assemblies, such as those described in U.S. Pat. No. 5,139,063, include arcuate wrapper assemblies that are mounted to the cover of the chipper and in relation to the cutting plane. Such assemblies, however, must be separately attached to the chipper, adding to the overall complexity and cost thereof.
It should be noted that the bedknife and feed spout are each susceptible to increased amounts of wear during use and may have to be replaced or serviced at various intervals. In addition, the bedknife disc or disc knives may also require adjustment in order to preserve the critical and extremely tight clearance relationship between the cutting edge of the bedknife and that of the plane of the blades of the rotary cutting disc. The positioning of the bedknife in relation to the blades of the cutting disc is critical with regard to the overall performance of the chipper. In this regard, replacement and/or adjustment of a bedknife is an extremely labor intensive and time consuming effort, requiring significant teardown of the apparatus. To that end, a number of attempts have been made in the prior art to reduce the effort involved. For example, according to U.S. Pat. No. 6,148,882, the patentee conceived the concept of a separate element that is introduced between the chipper frame and an external surface of the bedknife. This element is caused to move into place between the bedknife and the chipper frame wherein adjustment and/or replacement of the bedknife are facilitated. However, the use of such assemblies again requires the use of separate parts and added complexity and cost for purposes of operation.
Therefore, there is a general and perceived need to provide a bedknife for a disc chipper which can be maintained adjusted and/or replaced more easily than those previously in the field. There is also a general and perceived need in the field to improve the overall efficacy of cutting operations and throughput of disc chippers, including the elimination or substantial reduction of unwanted slivers.